Three-dimensional (3D) printing

ABSTRACT

Compositions including polyamides and methods of employing compositions including polyamides are described herein. For instance, composition for three-dimensional (3D) printing can include a polymer build material comprising of at least two polyamides including a first polyamide and a second polyamide, where the first polyamide is present in an amount ranging of from about 95% to about 99% of a total weight of the polymer build material and where the second polyamide is present in an amount ranging of from about 1% to about 5% of the total weight of the polymer build material.

PRIORITY INFORMATION

This application is a continuation of U.S. National Stage applicationSer. No. 16/490,917 filed on Sep. 4, 2019, which claims priority to theInternational Application No. PCT/US2017/062345 filed on Nov. 17, 2017.The contents of which are incorporated herein by reference in itsentirety.

BACKGROUND

Three-dimensional (3D) printing may be an additive printing process usedto make three-dimensional solid parts from a digital model. 3D printingmay be used in product prototyping, mold generation, mold mastergeneration, and manufacturing. Some 3D printing techniques areconsidered additive processes because they involve the application ofsuccessive layers of components. 3D printing may use annealing andfusing of the building material, which may be accomplished using lightpolymerization, thermal fusing, heat-assisted extrusion, melting, and/orchemical binding techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of examples of the present disclosure will become apparent byreference to the following detailed description and drawings, in whichlike reference numerals correspond to similar, though perhaps notidentical, components. For example, reference numeral 116 may refer toelement 116 in FIG. 1 and an analogous element may be identified byreference numeral 216 in FIG. 2 . For the sake of brevity, referencenumerals or features having a previously described function may or maynot be described in connection with other drawings in which they appear.

FIG. 1 is a simplified isometric view of an example of a 3D printingsystem disclosed herein.

FIGS. 2A, 2B, 2C, 2D, 2F, and 2E are schematic views depicting theformation of a patterned 3D printed object, a fused 3D printed object,and an extracted fused 3D printed object using examples of a 3D printingmethod disclosed herein.

FIG. 3 is a flow diagram illustrating an example of a 3D printing methoddisclosed herein.

FIG. 4 is a flow diagram illustrating an example of a method for makinga composition for three-dimensional (3D) printing disclosed herein.

FIG. 5 is a graph illustrating the elongation at break of 3D printedobjects using various polymer build materials.

FIG. 6 is a graph illustrating the elongation at break of 3D printedobjects using various polymer build materials in the xy printorientation.

FIG. 7 is a graph illustrating the elongation at break of 3D printedobjects using various polymer build materials in the z printorientation.

FIG. 8 is a microscopic image with crossed polarized lenses of a polymerbuild material comprising polyamide 12 and polyamide 11 taken at 100×magnification.

FIG. 9 is a microscopic image with crossed polarized lenses of a polymerbuild material comprising polyamide 12 taken at 100× magnification.

FIG. 10 is a microscopic image with crossed polarized lenses of apolymer build material comprising polyamide 12 and polyamide 11 taken ata magnification of taken at 500× magnification.

FIG. 11 is a microscopic image with crossed polarized lenses of apolymer build material comprising polyamide 12 taken at a magnificationof taken at 500× magnification.

DETAILED DESCRIPTION

In an example of an three-dimensional (3D) printing, a layer of apolymer build material (also referred to as build material particles) isexposed to radiation, but a selected region (in some instances less thanthe entire layer) of the polymer build material is fused and hardened tobecome a layer of a 3D part(s) or object(s).

An infrared radiation (IR) absorbing fusing agent (e.g., containingcarbon black as the IR absorbing species) can be selectively depositedon the selected region of the polymer build material. The fusingagent(s) is capable of penetrating into the layer of the build materialand spreading onto the exterior surface of the polymer build materialparticles. This fusing agent is capable of absorbing IR radiation andconverting the absorbed radiation to thermal energy, which in turn meltsor fuses the polymer build material that is in contact with the fusingagent. This causes the polymer build material to fuse to form the layerof the 3D part.

As used herein, the term “composition for 3D printing” refers to apolymer build material. In some examples the polymer build material cancomprise at least two polyamides. In some examples, the polymer buildmaterial can comprise at least two polyamides and at least onesemi-crystalline thermoplastic polymer.

As used herein, the term “3D printed object” refers to a patterned 3Dprinted object that has been exposed to a heating process, as detailedherein. It is understood that the polymer build material is patternedwith a fusing agent to achieve selective IR absorption or alter otherproperties. Moreover, it is to be understood that any polymer buildmaterial that is not patterned with the fusing agent is not consideredto be part of the patterned 3D object, even if it is adjacent to orsurrounds the patterned 3D object.

As used herein, the terms “fused 3D printed object” or “extracted fused3D printed object” each refer to the 3D printed object having beensubjected to a fusing temperature.

As used herein, the terms “3D printed part,” “fused 3D printed object”,“3D part,” “part,” “3D printed object,” “3D object,” or “object” may bea completed 3D printed part or a layer of a 3D printed part.

As used herein, the term “xy orientation” refers to printing the layersof a 3D printed object in the pull direction of the tensile specimen.

As used herein, the term “z orientation” refers to printing the layersof a 3D printed object perpendicular to the pull direction of thetensile specimen.

As used herein, “(s)” at the end of some terms indicates that thoseterms/phrases may be singular in some examples or plural in someexamples. It is to be understood that the terms without “(s)” may bealso be used singularly or plurally in many examples.

In some examples, polymer build material may be fused or annealed in thebuild area platform of the 3D printer. For example, the polymer buildmaterial may be exposed to elevated temperatures for extended periods oftime to form a 3D printed object. In some examples, polymer buildmaterial with high molecular symmetry may form larger crystalspherulites in 3D printed objects, which may appear more brittle. Insome examples, the addition of components in the polymer build materialthat reduce the system's symmetry may hinder the growth of crystalspherulites in 3D printed objects, may reduce embrittlement, and mayincrease the strain at break of the formed 3D printed object.

As such, a 3D printed object, as described herein, may rely on theaddition of components in the polymer build material to disrupt thematerial's crystal structure, reduce embrittlement, and increase thestrain at break.

Referring now to FIG. 1 , a simplified isometric view of an example of3D printing system 100 is depicted. It is to be understood that the 3Dprinting system 100 may include additional components and that some ofthe components described herein may be removed and/or modified.Furthermore, components of the 3D printing system 100 depicted in FIG. 1may not be drawn to scale and thus, the 3D printing system 100 may havea different size and/or configuration other than as shown therein.

The 3D printing system 100 includes a supply 114 of polymer buildmaterial 116; a build material distributor 118; an inkjet applicator 124for selectively dispensing a fusing agent 136 and a detailing agent 137;at least one heat source 132′, 132; a controller 128; and anon-transitory computer readable medium (not illustrated for ease ofillustration) having stored thereon computer executable instructions tocause the controller 128 to: utilize the build material distributor 118and the inkjet applicator 124 to iteratively form multiple layers (e.g.,layers 234 as depicted in FIG. 2B) of polymer build material 116 whichare applied by the build material distributor 118 and have received thefusing agent 136 and the detailing agent 137, as described herein,thereby creating a patterned 3D printed object (e.g., a patterned 3Dprinted object 242′ as depicted in FIG. 2E). In some examples, the atleast one heat source 132′, 132 can heat (e.g., heat 246 as illustratedin FIG. 2E) the patterned 3D printed object above the polymer buildmaterial 116 melt temperature, for instance, thereby substantiallyremoving solvents and/or co-solvent in the fusing agent and/or fusingthe polymer build material 116 (fusing the polymer build material andthe selectively applied fusing agent 136) to create a fused 3D printedobject.

As shown in FIG. 1 , the printing system 100 includes a build areaplatform 112, the build material supply 114 containing polymer buildmaterial 116, and the build material distributor 118.

The build area platform 112 receives the polymer build material 116 fromthe build material supply 114. The build area platform 112 may beintegrated with the printing system 100 or may be a component that isseparately insertable into the printing system 100. For example, thebuild area platform 112 may be a module that is available separatelyfrom the printing system 100. The build area platform 112 that is shownis also one example, and could be replaced with another support member,such as a platen, a fabrication/print bed, a glass plate, or anotherbuild surface.

The build area platform 112 may be moved in a direction as denoted bythe arrow 120, for instance, along the z-axis, so that polymer buildmaterial 116 may be delivered to the platform 112 or to a previouslyformed layer of polymer build material 116 (see arrow 220 as depicted inFIG. 2D). In an example, when the polymer build material 116 is to bedelivered, the build area platform 112 may be programmed to advance(e.g., downward) enough so that the build material distributor 118 canpush the polymer build material 116 onto the platform 112 to form alayer of the polymer build material 116 thereon (see, e.g., layer 234 asdepicted in FIGS. 2A and 2B). The build area platform 112 may also bereturned to its original position, for example, when a new part is to bebuilt.

The build material supply 114 may be a container, bed, or other surfacethat is to position the polymer build material 116 between the buildmaterial distributor 118 and the build area platform 112. In someexamples, the build material supply 114 may include a surface upon whichthe polymer build material 116 may be supplied, for instance, from abuild material source (not shown) located above the build materialsupply 114. Examples of the build material source may include a hopper,an auger conveyer, or the like. In some examples, the build materialsupply 114 may include a mechanism (e.g., a delivery piston) to move thepolymer build material 116 from a storage location to a position to bespread onto the build area platform 112 or onto a previously formedlayer of polymer build material 116.

The build material distributor 118 may be moved in a direction asdenoted by the arrow 122, for example, along the y-axis, over the buildmaterial supply 114 and across the build area platform 112 to spread alayer of the polymer build material 116 over the build area platform112. The build material distributor 118 may also be returned to aposition adjacent to the build material supply 114 following thespreading of the polymer build material 116. The build materialdistributor 118 may be a blade (e.g., a doctor blade), a roller, acombination of a roller and a blade, and/or any other device capable ofspreading the polymer build material 116 over the build area platform112. For instance, the build material distributor 118 may be acounter-rotating roller.

The polymer build material 116 may be any particulate polymer materialthat contains at least two polyamides. In some examples, the polymerbuild material 116 may be a powder. In some examples, discrete polymerbuild material 116 powder particles should no longer be visible in thefused 3D printed object. In some examples the powder may be formed from,or may include, short fibers that may, for example, have been cut intoshort lengths from long strands or threads of material

During fusing or melting the fusing agent 136, absorbs IR radiation,which causes portions of the polymer build material 116 that are coveredwith fusing agent to heat above the polymer build material's meltingtemperature, thus causing the polymer build material particles to meltand coalesce thereby forming one layer of a fused 3D printed object.

In some examples, the polymer build material 116 can comprise at leasttwo polymers, which can be a powder, a liquid, a paste, or a gel.Examples of polymer(s) can include semi-crystalline thermoplasticmaterials with a wide processing window of greater than 5° C. (e.g., thetemperature range between the melting onset and the re-crystallizationonset). In some examples, the polymer build material 116 can comprisepolymers that are miscible. Some specific examples of the polymer(s) caninclude polyamides (PAs) (e.g., PA 11/nylon 11, PA 12/nylon 12, PA6/nylon 6, PA 8/nylon 8, PA 9/nylon 9, PA 6,6/nylon 6,6, PA 612/nylon6,12, PA 8,12/nylon 8,12, PA 9,12/nylon 9,12, or combinations thereof).Other specific examples of the polymer(s) can include polyethylene andpolyethylene terephthalate (PET). Still other examples of buildmaterials can include polystyrene, polyacetals, polypropylene,polycarbonate, polyester, thermal polyurethanes, other engineeringplastics, and blends of any two or more of the polymers listed herein.Core shell polymer particles of these materials may also be used.

In various examples, the polymer build material 116 comprises at leasttwo polyamides. In some examples, the polymer build material 116 can bea combination of polyamide 12, polyamide 11, and at least onesemi-crystalline thermoplastic polymer with a wide processing window ofgreater than 5° C. In various examples, the polymer build material 116comprises polyamide 12 and polyamide 11. In some examples, polyamide 12and polyamide 11 make up 100% of the total weight of the polymer buildmaterial.

As used herein, the term “semi-crystalline” refers to a semi-crystallinematerial or a semi-crystalline polymer that contains organized andtightly packed molecular structures (crystalline domains) as well asrandomly assembled amorphous domains.

In various examples, a method for making a composition for 3D printingcan include polymer build material 116. In some examples, a method ofmaking a composition for three-dimensional (3D) printing can comprise:

dry blending a polymer build material comprising at least two polyamidesincluding a first polyamide and a second polyamide,

wherein the first polyamide is present in an amount ranging of fromabout 95% to about 99% of a total weight of the polymer build material,

wherein the second polyamide is present in an amount ranging of fromabout 1 to about 5% of the total weight of the polymer build material.

As used herein, the term “dry blending” refers to any process whichblends the components of the composition substantially uniformly.

The polymer(s) can have a melting point ranging from about 50° C. toabout 300° C. As examples, the polymer(s) may be a polyamide having amelting point of 190° C., or thermal polyurethanes having a meltingpoint ranging from about 100° C. to about 195° C., among otherpossibilities. In some examples, the polymer build material can have aglass transition temperature of from about 25° C. to about 125° C. andcan have a thermal decomposition temperature of from about 250° C. toabout 600° C. As used herein the term “glass transition temperature”refers to the temperature over which glass transition occurs. As usedherein the term “thermal decomposition temperature” refers to atemperature at which the substance chemically decomposes. The glasstransition temperature is lower than the thermal decompositiontemperature.

The polymer(s) can be made up of similarly sized particles ordifferently sized particles. In some examples, the polymer(s) caninclude particles of two different sizes. The term “size,” as usedherein with regard to the build material, refers to the diameter of aspherical particle, or the average diameter of a non-spherical particle(e.g., the average of multiple diameters across the particle). In anexample, the average size of the polymer(s) particles can range fromabout 0.1 μm to about 100 μm, or from about 1 μm to about 80 μm, or fromabout 5 μm to about 50 μm. As another example, the average particle sizeof the particles of the polymer build material 116 may range from about1 μm to about 200 μm.

In various examples, any polymer build material 116 may be used that isin powder form at the outset of the 3D printing method(s) disclosedherein. As such, the melting point, solidus temperature, and/orperitectic temperature of the polymer build material 116 may be abovethe temperature of the environment in which the patterning portion ofthe 3D printing method is performed (e.g., above 80° C. and/or above140° C.).

In various examples, a composition for 3D printing can include polymerbuild material 116. In some examples, a composition forthree-dimensional (3D) printing can comprise:

a polymer build material comprising at least two polyamides including afirst polyamide and a second polyamide,

wherein the first polyamide is present in an amount ranging of fromabout 95% to about 99% of a total weight of the polymer build material;and

wherein the second polyamide is present in an amount ranging of fromabout 1 to about 5% of the total weight of the polymer build material.

As mentioned, the first polyamide of the at least two polyamides can bepresent in an amount of from about 95% to about 99% of a total weight ofthe build material, among other possibilities. For instance, in someexamples, the first polyamide is present in the build material in anamount of from about 95 wt % to about 99 wt % based on the total weightof the build material, or from about 96 wt % to about 99 wt % based onthe total weight of the build material, or from about 97 wt % to about99 wt % based on the total weight of the build material, or from about98 wt % to about 99 wt % based on the total weight of the buildmaterial, or from about 96 wt % to about 98 wt % based on the totalweight of the build material, or from about 97 wt % to about 98 wt %based on the total weight of the build material, or less than about 99wt % based on the total weight of the build material, or less than about98 wt % based on the total weight of the build material, or less thanabout 97 wt % based on the total weight of the build material, or lessthan about 96 wt % based on the total weight of the build material, orgreater than about 95 wt % based on the total weight of the buildmaterial, or greater than about 96 wt % based on the total weight of thebuild material, or greater than about 97 wt % based on the total weightof the build material, or greater than about 98 wt % based on the totalweight of the build material.

As mentioned, the second polyamide of the at least two polyamides can bepresent in an amount of from about 1% to about 5% of a total weight ofthe build material, among other possibilities. For instance, in someexamples, the second polyamide is present in the build material in anamount of from about 1 wt % to about 5 wt % based on the total weight ofthe build material, or from about 2 wt % to about 5 wt % based on thetotal weight of the build material, or from about 3 wt % to about 5 wt %based on the total weight of the build material, or from about 4 wt % toabout 5 wt % based on the total weight of the build material, or lessthan about 5 wt % based on the total weight of the build material, orless than about 4 wt % based on the total weight of the build material,or less than about 3 wt % based on the total weight of the buildmaterial, or less than about 2 wt % based on the total weight of thebuild material, or greater than about 1 wt % based on the total weightof the build material, or greater than about 2 wt % based on the totalweight of the build material, or greater than about 3 wt % based on thetotal weight of the build material, or greater than about 4 wt % basedon the total weight of the build material.

As shown in FIG. 1 , the printing system 100 also includes an applicator124, which may contain the fusing agent 136 and the detailing agent 137disclosed herein. In some examples, the fusing agent 136 may includeother additives, depending, in part, upon the applicator 124 that is tobe used to dispense the fusing agent 136. The fusing agent 136 includesat least the liquid vehicle and the IR absorbing species. In someinstances, the fusing agent 136 comprises the liquid vehicle and the IRabsorbing species, without any other components.

As mentioned above, the fusing agent 136 includes the IR absorbingcompound (e.g. the pigment carbon black) and the liquid vehicle. As usedherein, “liquid vehicle” may refer to the liquid in which the IRabsorbing compound is dispersed to form the fusing agent 136. A widevariety of liquid vehicles, including aqueous and non-aqueous vehicles,may be used with the fusing agent 136. In some instances, the liquidvehicle comprises a solvent with no other components.

In other examples, the fusing agent 136 may include other ingredients,depending, in part, upon the applicator 124 that is to be used todispense the fusing agent 136. Examples of other suitable fusing agentcomponents include co-solvent(s), surfactant(s), antimicrobial agent(s),anti-kogation agent(s), viscosity modifier(s), pH adjuster(s) and/orsequestering agent(s). The presence of a co-solvent and/or a surfactantin the fusing agent 136 may assist in obtaining a particular wettingbehavior with the polymer build material 116.

The solvent may be water or a non-aqueous solvent (e.g., ethanol,acetone, n-methyl pyrrolidone, or aliphatic hydrocarbons). In someexamples, the fusing agent 136 comprises the IR absorbing compound andthe solvent (with no other components). In these examples, the solventmakes up the balance of the fusing agent 136.

Classes of organic co-solvents that may be used in the water-basedfusing agent 136 include aliphatic alcohols, aromatic alcohols, diols,glycol ethers, polyglycol ethers, lactams such as 2-pyrrolidone,caprolactams, formamides, acetamides, glycols, and long chain alcohols.Examples of these co-solvents include aliphatic alcohols, secondaryaliphatic alcohols, 1,2-alcohols, 1,3-alcohols, 1,5-alcohols, ethyleneglycol alkyl ethers, propylene glycol alkyl ethers, higher homologs(C₆-C₁₂) of polyethylene glycol alkyl ethers, N-alkyl caprolactams,unsubstituted caprolactams, both substituted and unsubstitutedformamides, both substituted and unsubstituted acetamides, and the like.

Examples of some suitable co-solvents include water-soluble high-boilingpoint solvents (i.e., humectants), which have a boiling point of atleast about 120° C., or higher. Some examples of high-boiling pointsolvents include 2-pyrrolidone (boiling point of about 245° C.),2-methyl-1,3-propanediol (boiling point of about 212° C.), andcombinations thereof. The co-solvent(s) may be present in the fusingagent 136 in a total amount ranging from about 1 wt % to about 50 wt %based upon the total wt % of the fusing agent 136, depending upon thearchitecture of the applicator 124.

Surfactant(s) may be used to improve the wetting properties and the flowproperties of the fusing agent 136. Examples of suitable surfactantsinclude a self-emulsifiable, nonionic wetting agent based on acetylenicdiol chemistry (e.g., SURFYNOL® SEF from Air Products and Chemicals,Inc.), a nonionic fluorosurfactant (e.g., CAPSTONE® fluorosurfactantsfrom DuPont, previously known as ZONYL FSO), and combinations thereof.In other examples, the surfactant is an ethoxylated low-foam wettingagent (e.g., SURFYNOL® 440 or SURFYNOL® CT-111 from Air Products andChemical Inc.) or an ethoxylated wetting agent and molecular defoamer(e.g., SURFYNOL® 420 from Air Products and Chemical Inc.). Still othersuitable surfactants include non-ionic wetting agents and moleculardefoamers (e.g., SURFYNOL® 104E from Air Products and Chemical Inc.) orwater-soluble, non-ionic surfactants (e.g., TERGITOL™ TMN-6 or TERGITOL™15-S-7 from The Dow Chemical Company). In some examples, it may beuseful to utilize a surfactant having a hydrophilic-lipophilic balance(HLB) less than 10.

Whether a single surfactant is used or a combination of surfactants isused, the total amount of surfactant(s) in the fusing agent 136 mayrange from about 0.01 wt % to about 10 wt % based on the total wt % ofthe fusing agent 136. In another example, the total amount ofsurfactant(s) in the fusing agent 136 may range from about 0.5 wt % toabout 2.5 wt % based on the total wt % of the fusing agent 136.

The liquid vehicle may also include antimicrobial agent(s). Suitableantimicrobial agents include biocides and fungicides. Exampleantimicrobial agents may include the NUOSEPT™ (Troy Corp.), UCARCIDE™(Dow Chemical Co.), ACTICIDE® M20 (Thor), and combinations thereof.Examples of suitable biocides include an aqueous solution of1,2-benzisothiazolin-3-one (e.g., PROXEL® GXL from Arch Chemicals,Inc.), quaternary ammonium compounds (e.g., BARDAC® 2250 and 2280,BARQUAT® 50-65B, and CARBOQUAT® 250-T, all from Lonza Ltd. Corp.), andan aqueous solution of methylisothiazolone (e.g., KORDEK® MLX from DowChemical Co.). The biocide or antimicrobial may be added in any amountranging from about 0.05 wt % to about 0.5 wt % (as indicated byregulatory usage levels) with respect to the total wt % of the fusingagent 136.

An anti-kogation agent may be included in the fusing agent 136. Kogationrefers to the deposit of dried fusing agent 136 on a heating element ofa thermal inkjet printhead. Anti-kogation agent(s) is/are included toassist in preventing the buildup of kogation. Examples of suitableanti-kogation agents include oleth-3-phosphate (e.g., commerciallyavailable as CRODAFOS™ O3A or CRODAFOS™ N-3 acid from Croda), or acombination of oleth-3-phosphate and a low molecular weight (e.g.,<5,000) polyacrylic acid polymer (e.g., commercially available asCARBOSPERSE™ K-7028 Polyacrylate from Lubrizol). Whether a singleanti-kogation agent is used or a combination of anti-kogation agents isused, the total amount of anti-kogation agent(s) in the fusing agent 136may range from greater than 0.20 wt % to about 0.62 wt % based on thetotal wt % of the fusing agent 136. In an example, the oleth-3-phosphateis included in an amount ranging from about 0.20 wt % to about 0.60 wt%, and the low molecular weight polyacrylic acid polymer is included inan amount ranging from about 0.005 wt % to about 0.03 wt %.

Buffer solutions may be used to control the pH of the fusing agent 136.From 0.01 wt % to 2 wt % of each of these components, for example, canbe used. Viscosity modifiers and buffers may also be present, as well asother known additives to modify properties of the fusing agent 136. Suchadditives can be present in amounts ranging from about 0.01 wt % toabout 20 wt %.

The detailing agent 137 includes an aqueous vehicle. As used herein,“aqueous vehicle” may refer to the aqueous fluid that enables thedetailing agent 137 to be delivered by the applicator 124. The detailingagent 137 includes a colorant that does not absorb the infraredradiation used for fusing. The detailing agent 137 may be appliedoutside of the edge boundary (i.e., the outermost portions where thefusing agent 136 is selectively deposited onto the build material during3D printing) of the 3D printed object during fusing. As such, thecolorant in the detailing agent does not contribute to the 3D printedobject growth, but rather contributes to edge acuity of the 3D printedobject.

The detailing agent 137 also serve to reduce the degree of coalescence,or prevent coalescence of a portion of the polymer build material 116 onwhich the detailing agent 137 has been delivered or has penetrated byproviding an evaporative cooling effect. The cooling effect of thedetailing agent 137 reduces the temperature of the polymer buildmaterial 116 containing the detailing agent 137 during fusing. Since thepolymer build material 116, with detailing agent 137 applied thereto,has a reduced temperature, the coalescence bleed may be reduced orprevented. As such, the detailing agent 137 contributes to thegeneration of dimensionally accurate 3D printed objects in real-timewithout the need for post-object mechanical refining processes (e.g.,tumbling, stone polishing, etc.).

In some examples, the detailing agent 137 may include other ingredients,depending, in part, upon the applicator 124 that is to be used todispense the detailing agent 137. Examples of other suitable detailingagent components include co-solvent(s), surfactant(s), anti-kogationagent(s), and/or biocide(s).

The presence of surfactant in the detailing agent 137 may assist inobtaining a particular wetting behavior with the polymer build material116. In some example, the surfactant may be any surfactant that has ahydrophilic-lipophilic balance (HLB) of less than 10. Examples ofsuitable surfactants include a self-emulsifiable, nonionic wetting agentbased on acetylenic diol chemistry (e.g., SURFYNOL® SEF from AirProducts and Chemicals, Inc.), a nonionic, acetylenic diol surfaceactive agent (e.g., SURFYNOL® 104 from Air Products and Chemicals,Inc.), a nonionic fluorosurfactant (e.g., CAPSTONE® fluorosurfactantsfrom DuPont, previously known as ZONYL FSO), a secondary alcoholethoxylate, nonionic surfactant (e.g., TERGITOL™ 15-S-9, TERGITOL™15-S-7, TERGITOL™ 15-S-5, each of which is available from The DowChemical Co.), a nonionic, ethoxylated low-foam wetting agent (e.g.,SURFYNOL® 440 from Air Products and Chemicals, Inc.), an ethoxylatedwetting agent and molecular defoamer (e.g., SURFYNOL® 420 from AirProducts and Chemicals, Inc.), an alkoxylated alcohol (e.g., TEGO® Wet510 from Evonik Industries AG), and combinations thereof.

Whether a single surfactant is used or a combination of surfactants isused, the total amount of surfactant(s) in the detailing agent 137 mayrange from about 0.02 wt % to about 1.00 wt % with respect to the totalweight of the detailing agent 137. In some example, the total amount ofsurfactant(s) in the detailing agent 137 may range from about 0.10 wt %to about 5.0 wt % based on the total wt % of the detailing agent 137.

The aqueous vehicle may also include co-solvent(s). The detailing agent137 also includes the co-solvent(s). The co-solvent is present in anamount ranging from about 3.00 wt % to about 5.00 wt % based on thetotal weight of the detailing agent 137. Some examples of suitableco-solvents include tetraethylene glycol, tripropylene glycol methylether, dipropylene glycol methyl ether, tripropylene glycol butyl ether,dipropylene glycol butyl ether, triethylene glycol butyl ether,1,2-hexanediol, 2-hydroxyethyl-2-pyrrolidinone, 2-pyrrolidinone,1,6-hexanediol, and combinations thereof.

As noted above, the detailing agent 137 may also include anti-kogationagent(s) and/or biocide(s). Examples of anti-kogation agents includeoleth-3-phosphate (e.g., CRODAFOS® N3 Acid from Croda) and a metalchelator, such as methylglycinediacetic acid (e.g., TRILON® M from BASFCorp.). Examples of suitable biocides include an aqueous solution of1,2-benzisothiazolin-3-one (e.g., PROXEL® GXL from Arch Chemicals,Inc.), quaternary ammonium compounds (e.g., BARDAC® 2250 and 2280,BARQUAT® 50-65B, and CARBOQUAT® 250-T, all from Lonza Ltd. Corp.), andan aqueous solution of methyl isothiazolone (e.g., KORDEK® MLX from TheDow Chemical Co.). When included, the anti-kogation agent may be presentin an amount ranging from about 0.5 wt % to about 1.5 wt %, and thebiocide may be present in an amount ranging from about 0.05 wt % toabout 2.0 wt %, each of which is with respect to the total weight of thedetailing agent 137.

The balance of the detailing agent 137 is water. As such, the amount ofwater may vary depending upon the amounts of dye, surfactant, andco-solvent, and in some instances anti-kogation agent and/or biocidethat are included.

The co-solvent and water of the detailing agent 137 provide evaporativecooling to the polymer build material 116 in proximity thereof (e.g., inthermal contact therewith). It is believed that evaporation of 1.3milligrams per cm² of the detailing agent 137 can remove up to 3 Joulesof energy per cm² of the polymer build material 116. This energy loss isenough to keep the polymer build material 116 from heating and fusing atthose portion(s) (240 as illustrated in FIG. 2C) where the detailingagent 137 is applied.

The applicator 124 may be scanned across the build area platform 112 inthe direction indicated by the arrow 126, for instance, along they-axis. The applicator 124 may be, for instance, an inkjet applicator,such as a thermal inkjet printhead, a piezoelectric printhead, or acontinuous inkjet printhead, and may extend a width of the build areaplatform 112. While the applicator 124 is shown in FIG. 1 as anindividual applicator, it is to be understood that the applicator 124may include multiple applicators that span the width of the build areaplatform 112. Additionally, the applicators 124 may be positioned inmultiple printbars. The applicator 124 may also be scanned along thex-axis, for instance, in configurations in which the applicator 124 doesnot span the width of the build area platform 112 to enable theapplicator 124 to deposit the fusing agent 136 and detailing agent 137over a large area of a layer of the polymer build material 116. Theapplicator 124 may thus be attached to a moving XY stage or atranslational carriage (neither of which is shown) that moves theapplicator 124 adjacent to the build area platform 112 in order todeposit the fusing agent 136 and detailing agent 137 in predeterminedareas of a layer of the polymer build material 116 that has been formedon the build area platform 112 in accordance with the method(s)disclosed herein. The applicator 124 may include a plurality of nozzles(not shown) through which the fusing agent 136 and the detailing agent137 are to be ejected.

The applicator 124 may deliver drops of the fusing agent 136 and thedetailing agent 137 at a resolution ranging from about 300 dots per inch(DPI) to about 1200 DPI. In some examples, the applicator 124 maydeliver drops of the fusing agent 136 and the detailing agent 137 at ahigher or lower resolution. The drop velocity may range from about 2 m/sto about 24 m/s and the firing frequency may range from about 1 kHz toabout 100 kHz. In one example, each drop may be in the order of about 10picoliters per drop, although it is contemplated that a higher or lowerdrop size may be used. For example, the drop size may range from about 1picoliter to about 400 picoliters. In some examples, applicator 124 isable to deliver variable size drops of the fusing agent 136 and thedetailing agent 137.

Each of the described physical elements may be operatively connected toa controller 128 of the printing system 100. The controller 128 maycontrol the operations of the build area platform 112, the buildmaterial supply 114, the build material distributor 118, and theapplicator 124. As an example, the controller 128 may control actuators(not shown) to control various operations of the 3D printing system 100components. The controller 128 may be a computing device, asemiconductor-based microprocessor, a central processing unit (CPU), anapplication specific integrated circuit (ASIC), and/or another hardwaredevice. Although not shown, the controller 128 may be connected to the3D printing system 100 components via communication lines.

The controller 128 may manipulate and transform data, which may berepresented as physical (electronic) quantities within the printingsystem's registers and memories, to control the physical elements tocreate the extracted fused 3D printed object 250 (As illustrated in FIG.2F). As such, the controller 128 is depicted as being in communicationwith a data store 130. The data store 130 may include data pertaining toa fused 3D printed object to be printed by the 3D printing system 100.The data for the selective delivery of the polymer build material 116,the fusing agent 136, and the detailing agent 137 may be derived from amodel of the fused 3D printed object to be formed. For instance, thedata may include the locations on each layer of polymer build material116 that the applicator 124 is to deposit the fusing agent 136 and thedetailing agent 137. In one example, the controller 128 may use the datato control the applicator 124 to selectively apply the fusing agent 136and the detailing agent 137. The data store 130 may also include machinereadable instructions (stored on a non-transitory computer readablemedium) that are to cause the controller 128 to control the amount ofpolymer build material 116 that is supplied by the build material supply114, the movement of the build area platform 112, the movement of thebuild material distributor 118, or the movement of the applicator 124.

As depicted in FIG. 1 , the printing system 100 may include a heater132′, 132. In some examples, the heater 132′ includes a furnace or oven,a microwave, or devices capable of hybrid heating (i.e.,convective/conductive heating and/or microwave heating). The heater 132′may be used for the patterned 3D printed object layer-by-layer, asdescribed herein.

In some example, the patterned 3D printed object 242′ can be exposed toheat such as heat provided by heater 132′. In some examples, the heater132′ may be a conductive heater or a radiative heater (e.g., infraredlamps, ultraviolet, or near-IR lamps, light emitting diodes (LED) or LEDarrays, flash lamps or visible light sources) that is integrated intothe system 100. These other types of heaters 132 may be placed below thebuild area platform 112 (e.g., conductive heating from below theplatform 112) or may be placed above the build area platform 112 (e.g.,radiative heating of the build material layer surface). Combinations ofthese types of heating may also be used. These other types of heaters132 may be used throughout the 3D printing process. In some examples,heater 132 may be used to maintain a constant bed temperature. In someexamples, heater 132 may be used to heat the build material supply 114and the build area platform 112 during the build process. In still someexamples, the heater 132′ may be a radiative heat source that ispositioned to heat each layer (e.g., layer 234 as depicted in FIG. 2C)after the fusing agent 136 and the detailing agent 137 have been appliedthereto. As depicted in FIG. 1 , the heater 132′ can be attached to theside of the applicator 124, which allows for printing and heating in anindividual pass. In some examples, both the heater 132 and the heater132′ may be used.

Referring now to FIGS. 2A through 2F, an example of the 3D printingmethod is depicted. Prior to execution of printing, the controller mayaccess data stored in the data store pertaining to a fused 3D printedobject 250 that is to be printed. The controller may determine thenumber of layers of polymer build material 216 that are to be formed,and the locations at which fusing agent 236 and the detailing agent 237from the applicator 224 are to be deposited on each of the respectivelayers.

In FIG. 2A, the build material supply 214 may supply the polymer buildmaterial particles 216 into a position so that they are ready to bespread onto the build area platform 212. In FIG. 2B, the build materialdistributor 218 may spread the supplied polymer build material 216 ontothe build area platform 212. The controller may execute control buildmaterial supply instructions to control the build material supply 214 toappropriately position the polymer build material 216, and may executecontrol spreader instructions to control the build material distributor218 to spread the supplied polymer build material 216 over the buildarea platform 212 to form a layer 234 of polymer build material 216thereon. As shown in FIG. 2B, one layer 234 of the polymer buildmaterial 216 has been applied.

The layer 234 has a substantially uniform thickness across the buildarea platform 212. In an example, the thickness of the layer 234 rangesfrom about 30 μm to about 300 μm, although thinner or thicker layers mayalso be used. For example, the thickness of the layer 234 may range fromabout 20 μm to about 500 μm. The layer thickness may be about 2× (i.e.,2 times) the particle diameter (as shown in FIG. 2B) at a minimum forfiner part definition. In some examples, the layer thickness may beabout 1.2× (i.e., 1.2 times) the particle diameter.

Referring now to FIG. 2C, selectively applying the fusing agent 236 on aportion 238 of the polymer build material 216 and selectively applyingthe detailing agent 237 on a portion 240 of the polymer build material216 continues. As illustrated in FIG. 2C, the fusing agent 236 and thedetailing agent 237 may be dispensed from the applicator 224. Theapplicator 224 may be a thermal inkjet printhead, a piezoelectricprinthead, or a continuous inkjet printhead, and the selectivelyapplying of the fusing agent 236 and the detailing agent 237 may beaccomplished by the associated inkjet printing technique. As such, theselectively applying of the fusing agent 236 and the detailing agent 237may be accomplished by thermal inkjet printing or piezo-electric inkjetprinting.

The controller (e.g., controller 128 as illustrated in FIG. 1 ) mayexecute instructions to control the applicator 224 (e.g., in thedirections indicated by the arrow 226) to deposit the fusing agent 236onto predetermined portion(s) 238 of the polymer build material 216 thatare to become part of a patterned 3D printed object 242′ and are toultimately be fused to form the extracted fused 3D printed object 250,as described herein. Similarly, the controller may execute instructionsto control the applicator 224 (e.g., in the directions indicated by thearrow 226) to deposit the detailing agent 237 onto predeterminedportion(s) 240 of the polymer build material 216 that are to become partof an unpatterned polymer build material.

The applicator 224 may be programmed to receive commands from thecontroller to deposit the fusing agent 236 according to a pattern of across-section for the layer of the fused 3D printed object 242 that isto be formed. As used herein, the cross-section of the layer of thefused 3D printed object 242 to be formed refers to the cross-sectionthat is parallel to the surface of the build area platform 212. In theexample shown in FIG. 2C, the applicator 224 may selectively apply thefusing agent 236 on those portion(s) 238 of the layer 234 that are to befused to become the first layer of the fused 3D printed object 242. Asan example, if the 3D part that is to be formed is to be shaped like acube or cylinder, the fusing agent 236 will be deposited in a squarepattern or a circular pattern (from a top view), respectively, on atleast a portion of the layer 234 of the polymer build material 216. Inthe example shown in FIG. 2C, the fusing agent 236 may be deposited in asquare pattern on the portion 238 of the layer 234 and not on theportions 240.

Similarly, the applicator 224 may be programmed to receive commands fromthe controller to deposit the detailing agent 237 on the layer ofpolymer build material. In the example shown in FIG. 2C, the applicator224 may selectively apply the detailing agent 237 on those portion(s)240 of the layer 234 that do not become part of the fused 3D printedobject 242 that is formed. As an example, if the 3D part that is to beformed is to be shaped like a cube or cylinder, the detailing agent 237will be deposited around a square pattern or around a circular pattern(from a top view), respectively, on at least a portion of the layer 234of the polymer build material 216. In the example shown in FIG. 2C, thedetailing agent 237 may be deposited on the portion 240 of the layer 234and not on the portion 238.

As mentioned above, the fusing agent 236 includes the IR absorbingpigment and the liquid vehicle. In some examples the fusing agent 236also includes the co-solvent (as or in addition to the liquid vehicle).In such examples, the co-solvent plasticizes the polymer particles andenhances the coalescing of the polymer particles upon exposure tophotonic energy in order to fuse the polymer build material particles216 together to form the patterned 3D printed object 242′. In variousexamples, the co-solvent (e.g., water) makes up the balance of thefusing agent 236.

In some examples, the co-solvent may be a lactone, such as2-pyrrolidinone or 1-(2-hydroxyethyl)-2-pyrrolidone. In some examples,the co-solvent may be a glycol ether or a glycol ether esters, such astripropylene glycol mono methyl ether, dipropylene glycol mono methylether, dipropylene glycol mono propyl ether, tripropylene glycol monon-butyl ether, propylene glycol phenyl ether, dipropylene glycol methylether acetate, diethylene glycol mono butyl ether, diethylene glycolmono hexyl ether, ethylene glycol phenyl ether, diethylene glycol monon-butyl ether acetate, or ethylene glycol mono n-butyl ether acetate. Insome examples, the co-solvent may be a water-soluble polyhydric alcohol,such as 2-methyl-1,3-propanediol. In some examples, the co-solvent maybe a combination of any of the examples above. In some examples, theco-solvent is selected from the group comprising 2-pyrrolidinone,1-(2-hydroxyethyl)-2-pyrrolidone, tripropylene glycol mono methyl ether,dipropylene glycol mono methyl ether, dipropylene glycol mono propylether, tripropylene glycol mono n-butyl ether, propylene glycol phenylether, dipropylene glycol methyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol mono hexyl ether, ethylene glycol phenylether, diethylene glycol mono n-butyl ether acetate, ethylene glycolmono n-butyl ether acetate, 2-methyl-1,3-propanediol, and a combinationthereof.

The co-solvent may be present in the fusing agent 236 in an amountranging from about 0.1 wt % to about 50 wt %, or from about 1.0 wt % toabout 40 wt %, or from about 10 wt % to about 30 wt % (based upon thetotal weight of the fusing agent 236). In some examples, greater orlesser amounts of the co-solvent may be used depending, in part, uponthe application architecture of the applicator 224.

When the fusing agent 236 is selectively applied in the targetedportion(s) 238, the fusing agent 236 selectively applied to the polymerbuild material 216 absorbs the heat emitted from the heater 232′,increasing the temperature of the polymer build material 216 and thefusing agent 236. The increase in temperature may cause the polymerbuild material particles 216 to fuse. The fusing of the polymer buildmaterial may cause the interstitial spaces to fill.

It is to be understood that portions 240 of the polymer build material216 do not receive the fusing agent 236 applied thereto and do notbecome part of the patterned 3D printed object 242′ that is ultimatelyformed.

The processes shown in FIGS. 2A through 2C may be completed and repeatedto iteratively build up several patterned layers and to form thepatterned 3D printed object 242′.

FIG. 2D illustrates the initial formation of a second layer of polymerbuild material 216 on the layer 234 patterned with fusing agent 236 anddetailing agent 237. In FIG. 2D, following deposition of the fusingagent 236 and the detailing agent 237 onto the layer 234 of polymerbuild material 216, the controller may execute instructions to cause thebuild area platform 212 to be moved a relatively small distance in thedirection denoted by the arrow 220. In other words, the build areaplatform 212 may be lowered to enable the next layer of polymer buildmaterial 216 to be formed. For example, the build material platform 212may be lowered a distance that is equivalent to the height of the layer234. In addition, following the lowering of the build area platform 212,the controller may control the build material supply 214 to supplyadditional polymer build material 216 (e.g., through operation of anelevator, an auger, or the like) and the build material distributor 218to form another layer of polymer build material 216 on top of thepreviously formed layer 234 with the additional polymer build material216. The newly formed layer may be patterned with the fusing agent 236.Similarly, the detailing agent 237 may be deposited on the newly formedlayer.

Referring back to FIG. 2C, the layer 234 may be exposed to heating usingheater 232′ after and/or during the depositing of the fusing agent 236and the detailing agent 237 to the layer 234 and before another layer isformed. The heater 232′ may be used during printing on a layer-by-layerbasis. In this example, the processes shown in FIGS. 2A through 2C(including the heating/fusing of the layer 234) may be repeated toiteratively build up several layers and to produce the fused 3D printedobject 242. It will be understood that the heaters 232′, 232 can be oneor both or a combination of overhead lamp(s) and/or lamps attached tomoving carriage(s) (not all options are shown in the figures).

The cycle time when printing layer-by-layer can range from about 5seconds to about 100 seconds. In some examples, the cycle time whenprinting layer-by-layer is at least 10 seconds. During this time, alayer of polymer build material 234 is formed, fusing agent 236 and thedetailing agent 237 are delivered to the layer, and heaters 232′, 232heat the surface of the polymer build material to a fusing temperaturethat fuses the polymer build material with selectively applied fusingagent 236 into the fused 3D printed object 242.

In some examples, layers of polymer build material 216 and fusing agent236 can be heated and fused on a layer-by-layer basis. It is understoodthat fusing occurs on a layer by layer basis. However, heat can beapplied on a layer-by-layer basis, every two layers, every three layers,or so forth to form the fused 3D printed object 242.

The patterned 3D printed object 242′ is a volume of the build materialcake 244 that is filled with the polymer build material 216 and thefusing agent 236. The remainder of the build material cake 244 is madeup of the unpatterned polymer build material 216.

As shown in FIG. 2E, the polymer build material 216 and fusing agent 236may be exposed to heat or radiation to generate heat, as denoted by thearrows 246. The heat applied may be sufficient to melt the polymer buildmaterial 216 and the fusing agent 236 into the patterned 3D printedobject 242′ and to produce a fused 3D printed object 242.

Heating the patterned 3D printed object 242′ above the melt temperatureor to a fusing temperature may result in the evaporation of asignificant fraction and in some instances all of the liquid from thepatterned 3D printed object 242′. The evaporated liquid may include anyof the fusing agent components. Liquid evaporation may result in somedensification, through capillary action, of the patterned 3D printedobject 242′.

Once fused, the fused 3D printed object 242 may then be extracted fromthe build material cake 244 to provide the extracted fused 3D printedobject 250 (as illustrated in FIG. 2F). The fused 3D printed object 242may be extracted by other means. In an example, the fused 3D printedobject 242 may be extracted by lifting the fused 3D printed object 242from the unpatterned polymer build material 216. An extraction toolincluding a piston and a spring may be used.

In some examples, the fused 3D printed object 242 may be cleaned toremove unpatterned polymer build material 216 from its surfaces. In someexamples, the fused 3D printed object 242 may be cleaned with a brushand/or an air jet. Some examples of cleaning procedures include rotarytumbling or vibratory agitation, ultrasonic agitation in a liquid,and/or bead blasting, among others.

During fusing using heat 246 from heat source 232′, the particles fromthe polymer build material may become fused and therefore form a fused3D printed object 242. That is, fusing the polymer build material 216with heat, is accomplished at a fusing temperature that is sufficient tofuse the particles in the polymer build material 216. The fusingtemperature is highly dependent at least upon the composition/particlesize of the polymer build material 216 and on the composition of thefusing agent. During heating/fusing, the fused 3D printed object 242and/or the patterned 3D printed object 242′ may be heated to atemperature above the melting point or the liquidus, or peritectictemperature of the polymer build material 216.

As detailed herein, a fusing temperature can be a temperature in a rangeof from about 80° C. to about 350° C. It is to be understood that thefusing temperature depends upon the polymer build material 216 that isutilized, and may be higher or lower than the described examples.Heating at a fusing temperature fuses at least the particles in thepolymer build material 216 to form a completed fused 3D printed object242. For example, as a result of fusing, the density may go from 50%density to over 90%, and in some cases very close to 100% of thetheoretical density.

FIG. 3 is a flow diagram illustrating an example of a 3D printing method360 disclosed herein. In this example, the method 360 of printing a 3Dprinted object can comprise adding a polymer build material comprisingat least two polyamides including a first polyamide and a secondpolyamide to a build material supply (362); selectively applying afusing agent on the build material (363); heating the build material andthe selectively applied fusing agent to a fusing temperature of fromabout 120° C. to about 350° C. (364); heating the build material andselectively applied fusing agent for at least 5 seconds (365); andcompleting (and in some examples repeating) 362, 363, 364, and 365 atleast one time to form the 3D printed object (366), as detailed herein.

FIG. 4 is a flow diagram illustrating an example of a method 470 formaking a composition for three-dimensional (3D) printing disclosedherein. In this example, the method 467 of making a composition forthree-dimensional (3D) printing can comprise dry blending a polymerbuild material (468) including at least two polyamides where the firstpolyamide is present in an amount ranging of from about 95% to about 99%of a total weight of the polymer build material and the second polyamideis present in an amount ranging of from about 1% to about 5% of thetotal weight of the polymer build material (469), as detailed herein.

Unless otherwise stated, any feature described hereinabove can becombined with any example or any other feature described herein.

In describing and claiming the examples disclosed herein, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly dictates otherwise.

It is to be understood that the ranges provided herein include thestated range and any value or sub-range within the stated range. Forexample, from about 0.5% to about 3% should be interpreted to includeother limits other than the explicitly recited limits of from about 0.5%to about 3%, but also to include individual values, such as about 0.8%,about 1.31%, about 2%, about 2.785%, about 2.95%, etc., and sub-ranges,such as from about 0.85% to about 2.35%, from about 1.21% to about2.95%, from about 1.5% to about 2.35%, etc. Furthermore, when “about” isutilized to describe a value, this is meant to encompass minorvariations (up to +/−10%) from the stated value.

Reference throughout the specification to “one example,” “someexamples,” “another example,” “an example,” and so forth, means that aparticular element (e.g., feature, structure, and/or characteristic)described in connection with the example is included in at least oneexample described herein, and may or may not be present in someexamples. In addition, it is to be understood that the describedelements for any example may be combined in various manners in thevarious examples unless the context clearly dictates otherwise.

Unless otherwise stated, references herein to “wt %” of a component areto the weight of that component as a percentage of the whole compositioncomprising that component. All amounts disclosed herein and in theexamples below are in wt % unless indicated otherwise.

If a standard test is mentioned herein, unless otherwise stated, theversion of the test to be referred to is the most recent at the time offiling this patent application. To further illustrate the presentdisclosure, examples are given herein. It is to be understood that theseexamples are described for illustrative reasons and are not to beconstrued as limiting the scope of the present disclosure.

Described herein, in some examples, is a method of printing athree-dimensional (3D) object, the method comprising

(A) adding a polymer build material comprising at least two polyamidesincluding a first polyamide and a second polyamide to a build materialsupply,

-   -   wherein the first polyamide is polyamide 12 and present in an        amount ranging of from about 95% to about 99% of a total weight        of the polymer build material; and wherein the second polyamide        is polyamide 11 and present in an amount ranging of from about        1% to about 5% of the total weight of the polymer build        material.

In some examples, is a method of printing a three-dimensional (3D)object, the method comprising

(A) adding a polymer build material comprising at least two polyamidesincluding a first polyamide and a second polyamide to a build materialsupply,

-   -   wherein the first polyamide is polyamide 12 and present in an        amount ranging of from about 95% to about 99% of a total weight        of the polymer build material; and    -   wherein the second polyamide is polyamide 11 and present in an        amount ranging of from about 1% to about 5% of the total weight        of the polymer build material;

(B) selectively applying a fusing agent on the polymer build material;

(C) heating the build material and the selectively applied fusing agentto a fusing temperature ranging of from about 120° C. to about 350° C.;

(D) heating the build material and the selectively applied fusing agentfor at least 5 seconds; and

(E) repeating (A), (B), (C), and (D) at least one time to form a 3Dprinted object.

In some examples, the fusing temperature is from about 80° C. to about350° C., 80° C. to about 205° C., 80° C. to about 200° C., or about 120°C. to about 350° C., or from about 120° C. to about 275° C., or fromabout 120° C. to about 250° C., or from about 120° C. to about 240° C.,or from about 120° C. to about 230° C., or from about 120° C. to about220° C., or from about 130° C. to about 210° C., or from about 140° C.to about 210° C., or from about 150° C. to about 200° C., or from about160° C. to about 200° C., or more than about 160° C., or more than about170° C., or more than about 180° C., or more than about 190° C., or morethan about 200° C., or at least about 150° C., or at least about 180°C., or at least about 190° C., or at least about 200° C.

In some examples, the melt temperature is from about 90° C. to about300° C., or from about 90° C. to about 250° C., or from about 90° C. toabout 200° C., or from about 90° C. to about 170° C., or from about 175°C. to about 300° C., or from about 180° C. to about 300° C., or fromabout 190° C. to about 300° C., or from about 175° C. to about 189° C.,or from about 200° C. to about 250° C., or less than about 250° C., orless than about 240° C., or less than about 210° C., or less than about200° C.

In some examples, (C) heating occurs in an ambient environment. However,in some examples, (C) heating occurs in an environment containing (i) avacuum or (ii) an inert gas, a low reactivity gas, a reducing gas, or acombination thereof. The inert gas, low reactivity gas, and reducing gascan include but are not limited to helium, argon, neon, xenon, krypton,nitrogen, hydrogen, carbon monoxide and combinations thereof.

To further illustrate the present disclosure, examples are given herein.It is to be understood these examples are provided for illustrativepurposes and are not to be construed as limiting the scope of thedisclosure.

EXAMPLES Example 1

Example 3D printed object were printed using a polymer build materialand a fusing agent. The polymer build material used to print the 3Dprinted object have the components as shown in Table 1, with the wt % ofeach component that was used.

TABLE 1 Example polymer build Components material (wt %) Polyamide 1295% Polyamide 11  5%

The fused 3D printed objects were formed by successively spreading 80 μmthick layers of polymer build material, followed by depositing printedareas with the fusing agent and non-printed areas with detailing agent.The fusing agent were applied by thermal inkjet, using 1-10 passprinting per layer, and after application the entire layer fused. Thebottom surface of the polymer bed was maintained at ˜165° C. byresistive heaters, and surface temperature of the build layersmaintained between 90° C.-165° C. Consecutive layers were printed andthen fused through the application of radiation via overhead halogenlamps. The 3D printed object was then extracted from the unpatternedpolymer build material and cleaned of unfused polymer material. Nofurther processing was performed. While the fusing agents were appliedby thermal inkjet, other forms of agent delivery, such as piezoelectricinkjet or continuous inkjet, could be employed. Fused 3D printed objectswith a thickness of approximately 4 millimeters were formed inaccordance with the procedure above.

The polymer build material was formed by dry blending a powder form ofpolyamide 12 and a powder form of polyamide 11 in the amounts describedabove. Polyamide 12 powder and polyamide 11 powder were placed in amixing barrel and mixed together. The Polyamide 12 powder and polyamide11 powder were mixed for approximately 2 hours to create a homogenizemixture.

Comparative Examples 1-5

Example 3D printed objects and fused 3D printed objects were printedusing the methodology of Example 1 but instead employed the polymerbuild material of Comparative Examples 1-5 having the properties asshown in Table 2.

TABLE 2 Comparative Example Example (WE) 1 (CE) 1 CE 2 CE 3 CE 4 CE 5 wt% 95% 100% 90% 80% 70% 50% Polyamide 12 wt %  5%  0% 10% 20% 30% 50%Polyamide 11 Annealing 165° C. 165° C. 165° C. 165° C. 165° C. 165° C.temperature (° C.) Annealing 0, 0.5, 0, 0.5, 0, 0.5, 0, 0.5, 0, 0.5, 0,0.5, time (hr) 1, 15 1, 15 1, 15 1, 15 1, 15 1, 15

FIG. 5 is a graph 570 illustrating the elongation at break of 3D printedobjects using various polymer build materials, including Example 1. Thepercent of the elongation at break of 3D printed objects printed withthe polymer build material of Example 1 and the polymer build materialin the Comparative Examples were tested. The percent of the elongationat break is listed on the y-axis (577) and the annealing time andmaterial is listed on the x-axis (578). The 3D objects were annealed ata temperature of at least 165° C. for 0 hours, 0.5 hours, 1 hour, and 15hours. Annealing was conducted in a convective oven.

FIG. 5 demonstrates that Example 1 (571) exhibits a higher strain atbreak than the Comparative Examples (572, 573, 574, 575, and 576) at 0hour, 0.5 hours, 1 hour, and 15 hours of annealing time. Example 1exhibited a strain at break of greater than 375% at 0 hours of annealingtime, greater than 150% at 0.5 hours of annealing time, of greater than200% at 1 hour of annealing time, and greater than 170% at 15 hours ofannealing time.

FIG. 6 is a graph 670 illustrating the elongation at break of a 3Dprinted objects using various polymer build materials in the xy printorientation, including Example 1. The percentage of the elongation atbreak of 3D printed objects printed with the polymer build material ofExample 1 and the polymer build material in Comparative Example 1 weretested. The percent of the elongation at break is listed on the y-axis(677) and the location and material is on the x-axis (678). Thepercentage of the elongation at break of the 3D printed objects weretested on 3D printed objects printed in different locations of the buildplatform (e.g., top, mid-top, mid-bottom, and bottom). The location inthe build platform determines the thermal environment and the time the3D printed object spends in the build platform after being printed. The3D printed objects were annealed at elevated temperature of from about165° C. for several hours in a 3D printer.

FIG. 6 demonstrates that Example 1 (671) exhibits a higher strain atbreak than Comparative Example 1 (672). Example 1 (671) exhibited astrain at break of greater than 24% for 3D printed parts printed in thetop of the build platform, greater than 19% for 3D printed parts printedin the mid-top of the build platform, greater than 19% for 3D printedparts printed in the mid-bottom of the build platform, and greater than21% for 3D printed parts printed in the bottom of the build platform.

FIG. 7 is a graph 770 illustrating the elongation at break of a 3Dprinted objects using various polymer build materials in the z printorientation, including Example 1. The percentage of the elongation atbreak of 3D printed objects printed with the polymer build material ofExample 1 and the polymer build material in the Comparative Example 1were tested. The percent of the elongation at break is listed on they-axis (777) and the location and material is listed on the x-axis(778). The percentage of the elongation at break of the 3D printedobjects were tested on 3D printed objects printed in different locationsof the build platform (e.g., top, mid-top, mid-bottom, and bottom). Thelocation in the build platform determines the thermal environment andthe time the 3D printed object spends in the build platform after beingprinted. The 3D printed objects were annealed at elevated temperature offrom about 165° C. for several hours in a 3D printer.

FIG. 7 demonstrates that Example 1 (771) exhibits a higher strain atbreak than Comparative Example 1 (772). Example 1 (771) exhibited astrain at break of greater than 16% for 3D printed parts printed in thetop of the build platform, greater than 14% for 3D printed parts printedin the mid-top of the build platform, greater than 14% for 3D printedparts printed in the mid-bottom of the build platform, and greater than14% for 3D printed parts printed in the bottom of the build platform.

FIG. 8 is a microscopic image 880 with crossed polarized lenses of thepolymer build material taken at 100× (100 times) magnification. In themicroscopic image 880, 200 micrometers (μm) of the polymer buildmaterial, Example 1, was placed on a glass slide and heated to 210° C.at a rate of 30° C./min until the polymer build material was completelymelted. The polymer build material was then cooled to 175° C. at a rateof 30° C./min and then slowly cooled to room temperature at 0.2° C./min.This temperature profile is similar to the thermal profile during theprinting process. The temperature profile also achieves high levels ofcrystallization similar to the printing process.

FIG. 9 is a microscopic image 990 with crossed polarized lenses of apolymer build material taken at 100× (100 times) magnification. In themicroscopic image 990, 200 micrometers (μm) of the polymer buildmaterial in Comparative Example 1, was placed on a glass slide andheated to 210° C. at a rate of 30° C./min until the polymer buildmaterial of Comparative Example 1 was completely melted. The polymerbuild material of Comparative Example 1 was then cooled to 175° C. at arate of 30° C./min.

FIG. 10 is a microscopic image 1080 with crossed polarized lenses of thepolymer build material taken at 500× (500 times) magnification. In themicroscopic image 1080, 200 micrometers (μm) of the polymer buildmaterial, Example 1, was placed on a glass slide and heated to 210° C.at a rate of 30° C./min until the polymer build material was completelymelted. The polymer build material was then cooled to 175° C. at a rateof 30° C./min.

FIG. 11 is a microscopic image 1190 with crossed polarized lenses of apolymer build material taken at 500× (500 times) magnification. In themicroscopic image 1190, 200 micrometers (μm) of the polymer buildmaterial in Comparative Example 1, was placed on a glass slide andheated to 210° C. at a rate of 30° C./min until the polymer buildmaterial of Comparative Example 1 was completely melted. The polymerbuild material of Comparative Example 1 was then cooled to 175° C. at arate of 30° C./min.

Referring now to FIGS. 8 and 9 , the microscopic image 880 of thepolymer build material in Example 1 depicts voids 882 in FIG. 8 .Similarly, the microscopic image 990 of the polymer build material inComparative Example 1 depicts voids 992 in FIG. 9 . FIG. 8 demonstratesthat there are less voids 882 in the polymer build material of Example 1in comparison to voids 992 of the polymer build material of ComparativeExample 1 in FIG. 9 . In some examples, a reduced amount of voids mayindicate a reduced amount of shrinkage in the formation of the 3Dprinted object. In some examples, a reduced amount of voids may alsoindicate a diminished degree of crystallization which may reduce theembrittlement of a 3D printed object.

Referring now to FIGS. 10 and 11 , the microscopic image 1080 of thepolymer build material in Example 1 depicts spherulites 1084 in FIG. 10. Similarly, the microscopic image 1190 of the polymer build material inComparative Example 1 depicts spherulites 1194 in FIG. 11 . FIG. 10demonstrates that the spherulites 1084 of the polymer build material inExample 1 are smaller in size in comparison to the spherulites 1194 ofthe polymer build material in Comparative Example 1 in FIG. 11 . Theaverage spherulite 1084 size of the polymer build material in Example 1of FIG. 10 ranges between 15 to about 20 μm. However, the averagespherulite 1194 size of the polymer build material in ComparativeExample 1 of FIG. 11 is about 30 μm. As mentioned above, smallerspherulites may reduce embrittlement of the formed 3D printed object,creating more elastic properties.

Prophetic Examples 1-4 providing compositions for three-dimensional (3D)printing are prophetic. The difference between Prophetic Examples 1-4and Example 1 is the composition of the polymer build material. Thus itis expected that Prophetic Examples 1-4 will yield similarcharacteristics as demonstrated by Example 1. As such, it is expectedthat the polymer build material of Prophetic Examples 1-4 would disruptthe material's crystal structure, reduce embrittlement, and increase thestrain at break.

Prophetic Example 1

Repeat the procedure in Example 1, except instead of using 5% ofpolyamide 11 and 95% of polyamide 12 to make up the total weight of thebuild material, use 4% of polyamide 11 and 96% of polyamide 12 to makeup the total weight of the build material.

Prophetic Example 2

Repeat the procedure in Example 1, except instead of using 5% ofpolyamide 11 and 95% of polyamide 12 to make up the total weight of thebuild material, use 3% of polyamide 11 and 97% of polyamide 12 to makeup the total weight of the build material.

Prophetic Example 3

Repeat the procedure in Example 1, except instead of using 5% ofpolyamide 11 and 95% of polyamide 12 to make up the total weight of thebuild material, use 2% of polyamide 11 and 98% of polyamide 12 to makeup the total weight of the build material.

Prophetic Example 4

Repeat the procedure in Example 1, except instead of using 5% ofpolyamide 11 and 95% of polyamide 12 to make up the total weight of thebuild material, use 1% of polyamide 11 and 99% of polyamide 12 to makeup the total weight of the build material. While several examples havebeen described in detail, it is to be understood that the disclosedexamples may be modified. Therefore, the foregoing description is to beconsidered non-limiting. As used herein, “(s)” at the end of some termsindicates that those terms/phrases may be singular in some examples orplural in some examples. It is to be understood that the terms without“(s)” may be also be used singularly or plurally in many examples.

What is claimed is:
 1. A build material for three-dimensional (3D)printing, the build material comprising: a polyamide 12 present in anamount from about 95 percent (%) to about 99% of a total weight of thebuild material; and a polyamide 11 present in an amount from about 1% toabout 5% of the total weight of the build material, wherein an averagespherulite size of the build material when annealed is less than anaverage spherulite size of the polyamide 12 when annealed.
 2. The buildmaterial of claim 1, wherein the total weight of the build material ismade up of the polyamide 12 and the polyamide
 11. 3. The build materialof claim 1, wherein the average spherulite size of the build materialwhen annealed is less than 30 micrometers (μm).
 4. The build material ofclaim 1, wherein the average spherulite size of the build material whenannealed is from about 15 μm to about 20 μm.
 5. The build material ofclaim 1, wherein the polyamide 12 is present in an amount of about 95%of the total weight of the build material.
 6. The build material ofclaim 1, wherein the polyamide 11 is present in an amount of about 5% ofthe total weight of the build material.
 7. The build material of claim1, wherein the polyamide 12, the polyamide 11, or both, aresemi-crystalline.
 8. A composition for three-dimensional (3D) printing,the composition comprising: a build material comprising: a polyamide 12present in an amount from about 95 percent (%) to about 99% of a totalweight of the build material; and a polyamide 11 present in an amountfrom about 1% to about 5% of the total weight of the build material,wherein an average spherulite size of the composition when annealed isless than 30 micrometers (μm).
 9. The composition of claim 8, wherein astrain at break of the composition when annealed is greater than astrain at break of a composition formed of the polyamide 12 whenannealed.
 10. The composition of claim 8, wherein an elongation at breakof the composition when annealed is greater than 20% as determined inaccordance with ASTM D638-14.
 11. The composition of claim 8, furthercomprising a fusing agent.
 12. The composition of claim 8, wherein thebuild material has a melt temperature ranging from about 175 degreesCelsius (° C.) to about 300° C.
 13. A composition for three-dimensional(3D) printing, the composition comprising: a build material comprising:a polyamide 12 present in an amount from about 95 percent (%) to about99% of a total weight of the build material; and a polyamide 11 presentin an amount from about 1% to about 5% of the total weight of the buildmaterial, wherein an average spherulite size of the composition afterprinting is less than 30 micrometers (μm).
 14. The composition of claim13, wherein the build material has an annealing temperature of about 165degrees Celsius.
 15. The composition of claim 13, wherein the polyamide12 is a polyamide 12 powder, the polyamide 11 is a polyamide 11 powder,and the build material is a substantially uniform dry mixture of thepolyamide 12 powder and the polyamide 11 powder.